Such a method is known from, for example, the Japanese Patent Application (Kokai) JP-A-1192155 laid open for public inspection and published in Pat. Abstr. of Japan, vol. 13, no. 483 (E-839) p. 161. in the manufacture of lead frames from a metal strip, the desired conductor pattern is obtained through stamping by means of a cutting tool which moves along the edge of an anvil. An undesirable side effect is that plastic deformation of the material, depending on the thickness and hardness of the material, causes rounded edges at the top where the cutting tool enters the metal, and projecting rims or burrs at the bottom, while the surface between the edges is not flat, but shows oblique facets.
To avoid these adverse side effects; those portions of the lead frame on which certain operations are to be carried out later, in particular the ends of the conductor tags on which the connection conductors to the crystal are to be applied by ultrasonic welding (or bonding), are freed from the irregularities described above by a cold-stamping or coining operation. This results in a flat and polished surface.
However, this involves the problem that the tension and compression forces occurring in the material during coining lead to deformation of both the upper and the lower side of the conductor ends. The result of this is that the conductor end thus processed no longer lies in the same plane as the remaining portion of the conductor tag after the operation, but encloses an angle with it. This angle is such that the coined conductor tip does not touch the heating block, but projects slightly upwards when, as is usual, the conductor tags are clamped with the non-coined portion against the heating block of the ultrasonic bonding device for the purpose of bonding. This means that not only does the conductor tip fail to come to the required temperature, but also that the exposed conductor tip acts as a damper for the ultrasonic energy. The result of this is that the connection with the crystal is not or is only imperfectly realised.